From 5a2990ff903cc4c4e7b72037b7ea9e4d0c74fafe Mon Sep 17 00:00:00 2001
From: Calum Lind <calumlind+deluge@gmail.com>
Date: Tue, 25 Sep 2018 11:41:15 +0100
Subject: [PATCH] [Core] Handle already prefetching magnet metadata

---
 deluge/core/core.py           | 11 ++++++++---
 deluge/core/torrentmanager.py |  5 +++++
 deluge/tests/test_core.py     | 19 ++++++++++++++++++-
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/deluge/core/core.py b/deluge/core/core.py
index 15024258e..51c9b1fe9 100644
--- a/deluge/core/core.py
+++ b/deluge/core/core.py
@@ -419,11 +419,16 @@ class Core(component.Component):
             The metadata is base64 encoded.
 
         """
-        def on_metadata(result):
+        def on_metadata(result, result_d):
             torrent_id, metadata = result
-            return torrent_id, b64encode(metadata)
+            result_d.callback((torrent_id, b64encode(metadata)))
+            return result
 
-        return self.torrentmanager.prefetch_metadata(magnet, timeout).addCallback(on_metadata)
+        d = self.torrentmanager.prefetch_metadata(magnet, timeout)
+        # Use a seperate callback chain to handle existing prefetching magnet.
+        result_d = defer.Deferred()
+        d.addBoth(on_metadata, result_d)
+        return result_d
 
     @export
     def add_torrent_file(self, filename, filedump, options):
diff --git a/deluge/core/torrentmanager.py b/deluge/core/torrentmanager.py
index cb5d1bb3f..484218ad4 100644
--- a/deluge/core/torrentmanager.py
+++ b/deluge/core/torrentmanager.py
@@ -316,6 +316,11 @@ class TorrentManager(component.Component):
 
         """
 
+        torrent_id = get_magnet_info(magnet)['info_hash']
+        if torrent_id in self.prefetching_metadata:
+            d = self.prefetching_metadata[torrent_id][0]
+            return d
+
         add_torrent_params = {}
         add_torrent_params['save_path'] = gettempdir()
         add_torrent_params['url'] = magnet.strip().encode('utf8')
diff --git a/deluge/tests/test_core.py b/deluge/tests/test_core.py
index 4fc23ab7c..b87f56500 100644
--- a/deluge/tests/test_core.py
+++ b/deluge/tests/test_core.py
@@ -11,7 +11,7 @@ from base64 import b64encode
 from hashlib import sha1 as sha
 
 import pytest
-from twisted.internet import defer, reactor
+from twisted.internet import defer, reactor, task
 from twisted.internet.error import CannotListenError
 from twisted.python.failure import Failure
 from twisted.web.http import FORBIDDEN
@@ -88,6 +88,8 @@ class CoreTestCase(BaseTestCase):
         self.rpcserver = RPCServer(listen=False)
         self.core = Core()
         self.core.config.config['lsd'] = False
+        self.clock = task.Clock()
+        self.core.torrentmanager.callLater = self.clock.callLater
         self.listen_port = 51242
         return component.start().addCallback(self.start_web_server)
 
@@ -311,6 +313,21 @@ class CoreTestCase(BaseTestCase):
         r2 = self.core.get_torrent_status(tid2, ['paused'])
         self.assertTrue(r2['paused'])
 
+    def test_prefetch_metadata_existing(self):
+        """Check another call with same magnet returns existing deferred."""
+        magnet = 'magnet:?xt=urn:btih:ab570cdd5a17ea1b61e970bb72047de141bce173'
+        expected = ('ab570cdd5a17ea1b61e970bb72047de141bce173', '')
+
+        def on_result(result):
+            self.assertEqual(result, expected)
+
+        d = self.core.prefetch_magnet_metadata(magnet)
+        d.addCallback(on_result)
+        d2 = self.core.prefetch_magnet_metadata(magnet)
+        d2.addCallback(on_result)
+        self.clock.advance(30)
+        return defer.DeferredList([d, d2])
+
     @defer.inlineCallbacks
     def test_remove_torrent(self):
         options = {}